Hyponatraemia and Brain Oedema in Newborns Following Oral Water Intoxication during Prolonged Labour

Severe pre-eclampsia as a rare cause of profound hyponatraemia

Profound hyponatraemia, defined as sodium <125 mmol/L, is a very rare complication of pre-eclampsia (PET) with a relative paucity of cases reported. Pre-eclampsia is a multisystem disorder with a maternal mortality of up to 20%. Hyponatraemia is associated with disease severity, twin pregnancy, advanced maternal age, in vitro fertilisation and HELLP (haemolysis, elevated liver enzymes and low platelets). The authors present the case of a low-risk nulliparous woman presenting with frontal headache and normal BP at 31+2 weeks gestation. Laboratory investigations confirmed a sodium of 123 mmol/L. Her urine protein creatinine ratio was 322 mg/mmol. She developed PET (BP 171/100 mm Hg) refractory to pharmacological management. She underwent an emergency lower segment caesarean section and was delivered of a live neonate. The maternal serum sodium normalised within 24 hours. Hyponatraemia should be regarded as a marker of severity in the setting of pre-eclampsia and may be an indication for an expedited delivery. Prompt management is required to prevent convulsions, maternal mortality and adverse fetal outcomes.

A Case Report of Preeclampsia Causing Severe Hyponatremia: Rare or Rarely Reported?

Preeclampsia presenting as severe hyponatremia is an enigma of modern obstetric practice. The hyponatremia can cause severe maternal neurological morbidity, including cerebral edema and seizures. Neonates, with serum sodium reflecting maternal levels, are also at risk. Despite this, the literature remains ambiguous about its incidence, the pathophysiology is poorly understood, and guidelines on preeclampsia (including those of the American College of Obstetricians and Gynecologists) do not discuss the issue. This case of preeclampsia associated with severe hyponatremia in a laboring woman highlights these issues.

Feto-maternal osmotic balance at term. A prospective observational study

OBJECTIVE

We performed the present study to investigate the feto-maternal osmotic relationship at term with the hypothesis that, in contrast to the literature, maternal plasma osmolality is lower than fetal levels. In a previous study, we found that maternal plasma sodium at delivery was consistently lower than the sodium in the umbilical artery. Our aim was to corroborate these results with analysis of osmolality.

METHODS

Blood was sampled from 30 women immediately before cesarean section and from the umbilical artery and vein before cord clamping and osmolality, sodium and albumin were analyzed.

RESULTS

Maternal osmolality was (mean; 95% confidence interval) 287.0 (285.8-288.2) mOsmkg/kg, arterial cord osmolality was 289.4 (287.9-291.0) mOsm/kg and venous cord osmolality was 287.3 (286.0-288.5) mOsm/kg. The paired difference between maternal and umbilical arterial osmolality was mean (SD) -2.4 (3.3) mOsm/kg (P<0.001), between maternal and umbilical vein -0.3 (3.0) mOsm/kg (P=0.63) and between umbilical artery and vein -2.1 (2.8) mOsm/kg (P<0.001).

CONCLUSION

Maternal osmolality was significantly lower than arterial cord osmolality confirming our previous results. The feto-maternal osmotic gradient favors water transport from the mother to the fetus and may increase the fetal risk of water intoxication when the mother ingests or is administered large volumes of electrolyte free solutions.

The healthy newborn hydration model: a new model for understanding newborn hydration immediately after birth

The normal small volume of breast milk produced in the first 2 days following birth may raise concerns about adequate hydration in breast-fed newborns. These concerns are further magnified when breast-fed infants lose ≥7% of their birth weight within 2 days postnatally. Weight loss following birth is presumably mostly water loss that could result in hypohydration and subsequent hypernatremic dehydration. However, excess fluid loss immediately following birth is a normal and necessary process. Furthermore, newborns exposed to excess fluid intake during labor may need to lose ≥7% of birth weight in the first 2 days following birth in order to achieve euhydration. Normal newborn fluid loss following birth confounds the use of weight loss as the sole measure of newborn hydration. We thus propose the healthy newborn hydration model that highlights the normalcy of newborn weight loss immediately following birth and the healthy newborn's compensatory mechanisms for preserving adequate hydration. We also recommend the use of serum sodium to measure intravascular osmolarity in addition to monitoring weight loss to obtain a more comprehensive newborn hydration assessment. Research is necessary in healthy newborns to identify relationships among fluids received in utero, newborn weight loss, and hydration, as evaluated with laboratory measures, in the first 2 days following birth. This information will guide clinicians in correctly identifying newborns with inadequate hydration who are in need of supplementary fluids versus newborns with adequate hydration for whom exclusive breast-feeding can be supported and encouraged.